Device for visual positioning

ABSTRACT

A device for visual positioning of the type including a fixed scale ( 2 ), arranged on a base ( 1 ), defining an axis (Y), for pointing at a first landmark ( 5 ), at least two moving scales ( 6, 7 ), generating the axes (X, Z), concurrent with the axis (Y), for pointing at other landmarks ( 10, 13 ), jointed about an assembly piece ( 22 ), fixed to the base ( 1 ), provided with a hole ( 14 ) in the centre thereof, at least one steerable plate ( 15 ) or a steerable prism on a pivot, inserted in a fixed manner into said hole ( 14 ). The plate ( 15 ) or the prism permits a simultaneous direct sighting of the first landmark ( 5 ) and a reflected sighting of at least one of the other landmarks ( 10, 13 ). The invention is characterised in including elements for facilitating and speeding up the positioning of the axes (X, Y, Z), following or simultaneous to the orientation of the plate ( 15 ) or prism.

The present invention relates to devices intended for visualself-positioning according to the method of subtended arcs, making itpossible both to observe the angular deviations between the landmarksand the plotting of the corresponding position on the map.

The device according to the invention is a refinement of the inventiondescribed in documents FR-A-1 450 588 and U.S. Pat. No. 3,410,642.

For the safety of navigation, it is out of the question to rely only onelectronic positioning technologies. Despite apparent precision, anautomatic system may give false indications that are difficult todiscern inside the system itself. It remains subject to emissions ofsignals prone to faults or to anomalies of propagation. The user isexposed to errors of agreement of the coordinate systems used. Thereceiver apparatus may be damaged, fall into the water. It is thereforestill necessary to be able to cross check the information originatingfrom several independent systems (radio navigation, astronomicalnavigation, reckoning, sounding lines, bearings).

In sight of land, entitled to no longer believe anything other than whathe sees when the dangers multiply, the navigator deterred from thepractice of taking cross bearings, on account of the manifest facilitiesoffered by electronic devices, often encounters difficulties indetermining the corrections of the compass or of the terrestrialmagnetic field, applying them east or west, reading and plotting thebearings. At worst, he compounds the errors, at best, he compounds thelack of precision.

Relatively inexpensive, foolproof, requiring no source of energy, purelyoptical and manual devices shelter the user from such errors oruncertainties. In addition to checking the plausibility of the othersystems used, they allow extremely reliable and precise positioning.Their simplicity earns them their rightful place on board alongsidesophisticated technologies based on electronics.

A problem which arises during the use of these optical devices lies inthe difficulties encountered in observing by reflected vision.

The device described in FR-A-1 450 588 and U.S. Pat. No. 3,410,642remedies same, and allows both the observation of the position and itsplotting on the map. It consists essentially of three superposed,orientable transparent scales each furnished with an end foresight, andwith a plate (mirror) pivoting perpendicularly to the plane of thescales at the intersection of their sighting axes. The plate hastransparent and reflecting portions, a vertical edge of the transparentportion being aligned with the axis of rotation of the plate and of thescales.

Observation is done in two stages, based on two lateral landmarkssituated on either side of a central landmark. The image in the mirrorof a first lateral landmark is brought onto the central landmark placedin direct line of sight on the central axis, by orientation of thepivoted mirror, then the lateral axis is aligned with the central axisby searching for it in the mirror of the plate and by superposing thetwo foresights. The operation is repeated for the second laterallandmark.

The alignment of the lateral scale does not modify the prior orientationof the mirror, since the assembly piece of the three scales constitutesa gudgeon for the pivoted plate and is integral with the central scale.

The axes being fixed in position with fastening studs, the removablepivoted plate is detached so as to apply the axes to the map, makingthem pass through the points locating the corresponding landmarks, andthe position of the boat is plotted at their intersection in the orificeof the gudgeon.

U.S. Pat. No. 4,245,393 and U.S. Pat. No. 4,383,372 were granted to aninvention allowing the simultaneous observation of the three landmarksby a device similar to the previous one in certain aspects.

These documents describe two embodiments. The first has the particularfeature of dispensing with any mirror. The second comprises, in order toobserve by reflected vision, not one mirror at the center, but a mirrorof sextant type on each of the lateral scales and two target mirrors onthe central scale, sending the images to a common eyepiece on the rearof the central scale.

The mirrorless device suffers from insufficient precision, the eye beingunable to position itself exactly at the point of convergence and tosight satisfactorily at one and the same time along the three axes. Inthe other case, the multiplying up of the mirrors added to thecompulsory passage through an eyepiece considerably reduces the field ofvision.

The configuration with one mirror placed at the intersection of thethree sighting axes as advocated by FR-A-1 450 588 and U.S. Pat. No.3,410,642 advantageously makes it possible, in order to find and retainthe image in the mirror, to have recourse to just one reflection. Inrespect of this same advantage it makes it possible to dispense with theeyepiece since the boundary between its transparent part and itsreflecting part serves therefor when sighting along the three axes.

The purpose of the invention is to propose a refinement of this deviceaimed at facilitating the use thereof, and at curtailing the durationrequired for taking the bearing of a position.

Accordingly the subject of the invention is a device for visualpositioning, of the type comprising a fixed scale mounted on a basedefining an axis (Y), intended to be pointed toward a first landmark, atleast two movable scales demarcating axes (X, Z) concurrent with theaxis (Y) and intended to be pointed toward other landmarks, articulatedabout an assembly piece fixed to the base provided at its center with aperforation, at least one orientable plate or an orientable prismmounted on a pivot inserted in a removable manner in said perforation,said plate or said prism allowing simultaneously direct sighting of thefirst landmark and reflected sighting of at least one of the otherlandmarks, characterized in that it comprises means for facilitating andcurtailing the positioning of the axes (X, Y, Z) subsequent to orsimultaneously with the orientation of the plate or of the prism.

Said fixed scale may be placed between two movable scales.

Said means for facilitating and curtailing the positioning of the axesmay be constituted by a graduated ring fashioned on the periphery of thebase.

Said means may be constituted by means making it possible to slave therotation of said movable scales to the rotation of the at least oneplate or prism.

Said means making it possible to slave the rotation of the movablescales to the rotation of the at least one plate or prism may thencomprise notched sectors carried by the movable scales, notched wheelsassociated with said notched sectors, and at least one notched wheelthat can be rendered integral with the plate or with the prism andassociated with at least one pinion that can be meshed with one or otherof the notched sectors.

The device may comprise a number of plates or prisms, of notched wheelsand of pinions which is equal to the number of movable scales.

Said plate may comprise a recessed part, of which an edge is situated onthe axis of articulation (T) of the movable scales and a reflecting parton at least one of its faces.

Said plate may be both transparent and reflecting over the whole of itssurface.

Said scales may comprise foresights situated on said axes.

As will have been understood, the present invention is thereforedirected at means of associating the orientation of the movable scaleswith that of the mirror-forming plate or the prism in a simple andeffective manner so as to find easily, or even automatically, theforesight of the movable scale in the field of the mirror. This makes itpossible to facilitate and curtail the plotting of the position. Theshortening of the duration of the plot makes it possible to decrease theerrors that may originate from an appreciable variation in the positionof the boat during the plotting operation itself.

According to a first embodiment, the orientation of the mirror or of theprism not being tied to those of the scales, a graduated ring printed onthe base integral with the fixed scale and on which the movable scalespivot makes it possible to place the axis of the movable scalesymmetrically with the axis of the fixed scale with respect to themirror or to the prism, so as to easily find its foresight there andcomplete the alignment of the scale if necessary.

According to a second embodiment, the device according to the inventioncomprises a mechanism for slaving the orientation of each moveable scaleto that of the mirror or of the prism, for example by wheels and sectorslinked without slippage by notchings or other devices playing the samerole, be this by friction of adhesive materials or by belts.

The invention will be better understood on reading the description whichfollows, given with reference to the following appended figures:

FIG. 1 which represents, seen in perspective, the general principle of adevice to which the invention applies;

FIG. 2 which represents, seen from above, a first exemplary deviceaccording to the invention;

FIG. 3 which represents, seen from above, a second exemplary deviceaccording to the invention;

FIG. 4 which represents seen in profile a detail of the device of FIG.3.

FIG. 1 recalls the general principle of the design of a device that theinvention aims to improve. It comprises a circular base 1 carrying acentral fixed scale 2, of which a straight edge 3 defines a fixed axisY. The end of the fixed scale 2 carries a foresight 4 placed on the Yaxis and intended for sighting a first landmark 5 termed the centrallandmark. Articulated about the central region of the base 1 and able toturn about an axis T passing through the center of the base 1 are twosuperposed lateral movable scales 6, 7. The first movable scale 6 has astraight edge 8 defining an X axis and carries at its end a foresight 9placed on the X axis for sighting a first lateral landmark 10. Thesecond movable scale 7 has, likewise, a straight edge 11 defining a Zaxis and a foresight 12 placed on the Z axis for sighting a secondlateral landmark 13. At its center, where the axes (X, Y, Z) cross, thebase 1 comprises an orifice 14 into which may be inserted rotatably arod carrying a plate 15. This plate 15 is preferably oval (asrepresented) rather than rectangular, so as to increase the field ofvision when sighting and to decrease wind resistance. It comprises arecess 16 allowing direct sighting of the central landmark 5, and a side17 of which coincides with the axis T. The remainder of the plate 15 isconstituted by a reflecting surface 18 where the lateral landmarks 10,13 may be reflected. This recessed/reflecting plate 15 could be replacedwith any other type of device affording the same functions, such as aprism or a uniformly semitransparent plate. The mode of use of thisdevice was recalled in the introduction to this text.

In FIGS. 2 and 3, the plate 15 has been omitted for greater clarity.

According to the first variant of the invention, represented in FIG. 2,the periphery of the base 1 carries a graduated ring 19 making itpossible to determine the angular offset between the Y axis and theplate 15 on the one hand, the X axis and the Z axis on the other hand.In this way, when the user has determined the angular position of theplate 15 which allows him to superpose the central landmark 5 with thereflection of one of the lateral landmarks 10, 13, the graduated ringallows him to read the value of the angle θ formed by the X axis and theplate 15. The user then places that one of the movable scales 6, 7,which corresponds to the lateral landmark 10, 13 which has been sighted,at the angular position 20. Normally, he ought then to immediatelyobtain the superposition of the corresponding foresight 9, 12 with thecentral landmark 5. In addition, just a slight alteration of the angularposition of the movable scale 6, 7 is necessary in order to hone theadjustment. This simple operation makes it possible to shorten the timedevoted to the fine sighting of the lateral landmarks 10, 13. After eachsighting, the position of the corresponding movable scale 6, 7 is lockedon the base by means of a thumbwheel 20, 21. The plate 15 is thenremoved from the orifice 14, and the device is placed on the map in sucha way that the X, Y, Z axes each pass through the positions of theirrespective landmarks 10, 5, 13. The position of the boat is given by thelocation on the map of the center of the orifice 14.

According to the second embodiment, represented in FIGS. 3 and 4, therotation of the moveable scales 6, 7 is alternately slaved to that ofthe plate 15. In this way, the correct angular position of each movablescale 6, 7 is obtained simultaneously with the obtaining of thesuperposition of the central landmark 5 with the reflection of thecorresponding lateral landmark 10, 13, and no alteration is necessary.

According to a nonlimiting example, the assembly piece 22 for thescales, the upper part of which serves as gudgeon for the plate 15, isrepresented with the same diameter as the ends of the movable scales 6,7 sliding one on the other and comprising a notched sector 23. Thesenotched sectors 23 are associated at their level with notched wheels 24of like diameter. The orientable plate 15 is integral with a notchedwheel 25 associated with a pinion 26. They are dimensioned for examplein a ratio of one to two. The pinion 26 integral with its pin has twopossible positions by translation along its axis, interchangeable whenthe X and Z axis are superposed. It remains meshed with the notchedwheel 25 in one or the other position. The purpose of the translation isto engage the notched sector of one or the other scale 6, 7 with the pinof the pinion 26. To change movable scale 6, 7 after the firstobservation, the lateral axes X and Z are again superposed. The plate 15is reset in position with the lateral axis X and the central axis Zsuperposed. Its reflecting surface 18 is advantageously fashioned on thetwo faces of the plate 15 so as not to have to turn it over. Themechanism is preferably partially encased in a shell (not represented)integral with the assembly piece for the movable scales 6, 7 and thebase 1 on the central scale 2. The shell passes under the notched wheel25 of the plate 15 and under the pinion 26 regardless of its position.This shell comprises, as well as the base 1, a journal for the commonpin shared by the pinion 26 and the notched wheels 24.

The observation is done is two stages, the plate 15 drives one or theother of the movable scales 6, 7 until there is superposition of thecentral landmark 5 and of the central foresight 4 by direct sightingwith the lateral landmark 10 or 13 and of the lateral foresight 9 or 12by reflected sighting. The two movable scales 6, 7 having been fixed inposition with the thumbwheels 20, 21 and the plate 15 having beenremoved, the three axes X, Y, Z are made to pass through the positionscorresponding on the map to the landmarks 5, 10, 13 observed, and thepencil is introduced into the orifice 14 of the gudgeon in order to plotthe position at their intersection.

The refinement pertains also to the plate 15 whose function isessentially to simultaneously ensure a direct view and a reflected viewas well as to demarcate the axes of sighting at their intersection.Apart from using a semitransparent material (both transparent andreflecting) or a prism simultaneously allowing both views in asatisfactory manner, according to a nonlimiting embodiment, it hasadvantageously been possible to reduce the field of direct view to thebenefit of the field of reflected view, by extending the reflectingsurface 18 on both sides of the axis T. The reflecting surface 18 ispreferably present on both sides of the axis affording a direct view ofone or more transparent or recessed surfaces 16, the axis of direct viewremaining demarcated by the boundary 17 between transparent part 16 andreflecting part 18. Initial usage may be facilitated, for however muchtime it takes to become accustomed thereto, by a larger plate 15 whosemain drawback is wind resistance.

The X, Y, Z axes being unable to be applied to the map along their wholelength, the scales 5, 6, 7 being superposed, better than by transparencyor through a groove, their axes demarcated by one of the sides 3, 8, 11of the scales 2, 6, 7, slit vertically, may be superposed with thelandmarks 5, 10, 13 on the map with no parallax error. This also allowsthe use of pegs as an aid in guiding the search for conjunction of thepassage of the three axes X, Y, Z through the three landmarks 10, 5, 13.

The scales 2, 6, 7 are preferably of slightly different lengths so as toorient them on one and the same axis without coming into abutmentagainst the foresights 4, 9, 12.

According to a nonlimiting embodiment or mode of use of the deviceaccording to the invention, observation is carried out on threelandmarks 5, 10, 13 in two stages, on either side of the centrallandmark 5, the observation of additional landmarks being carried outthrough new operations. Without departing from the spirit of thisinvention the addition of one or more further scales is possible so asto observe further landmarks in one and the same operation.

Simultaneous observation of the three landmarks 5, 10, 13 is alsopossible in accordance with the invention by superposing two plates thatcan be oriented independently of one another, the sighting marks at theend of the scales advantageously being raised up so as, very rigorously,to sight in two parallel planes. The lower plate is in two partsassembled on a tube at the center is mounted on a pivot of annularsection. It permits passage of the cylindrical pivot of the upper platein its sighting axis and in its pivot.

The association of the rotation of the plates with that of thecorresponding movable scale is effected in the same manner with the aidof the notched ring. The slaving of the orientation of the movablescales to that of their plate each furnished with a drive wheel isobtained through a mechanism similar to that shown diagrammatically inFIG. 4, independent for each scale and arranged on each side of thefixed scale, the movable scales being redesigned so that this newarrangement does not impede their orientation.

Other devices for slaving the position of the movable scales to theorientation of the plate or plates other than that which has beendescribed are conceivable. Such devices could for example use belts orfriction surfaces rather than notches.

The device may, without departing from the boundaries of the invention,accommodate graduations intended for uses other than positioning by themethod of subtendable arcs, such as proportional compasses orprotractors.

In the variant described and represented, the movable scales flank thefixed scale (which is materially solid with the base but could also be apiece added onto the base). However this arrangement is not compulsory:the movable scales could very well be situated on the same side of thefixed scale. It would then no longer be justifiable to speak of “centrallandmark” and “lateral landmarks”, but it would then be possible tospeak, in general, of “first landmark” to designate the landmark sightedby the axis of the fixed scale and of “other landmarks” to designate thelandmarks sighted by the axes of the movable scales.

1. A device for visual positioning, of the type comprising a fixed scale (2) mounted on a base (1) defining an axis (Y), intended to be pointed toward a first landmark (5), at least two movable scales (6, 7) demarcating axes (X, Z) concurrent with the axis (Y) and intended to be pointed toward other landmarks (10, 13), articulated about an assembly piece (22) fixed to the base (1) provided at its center with a perforation (14), at least one orientable plate (15) or an orientable prism mounted on a pivot inserted in a removable manner in said perforation (14), said plate (15) or said prism allowing simultaneously direct sighting of the first landmark (5) and reflected sighting of at least one of the other landmarks (10, 13), characterized in that it comprises means for facilitating and curtailing the positioning of the axes (X, Y, Z) subsequent to or simultaneously with the orientation of the plate (15) or of the prism.
 2. The device as claimed in claim 1, characterized in that said fixed scale (2) is placed between two movable scales (6, 7).
 3. The device as claimed in claim 1, characterized in that said means for facilitating and curtailing the positioning of the axes (X, Y, Z) are constituted by a graduated ring (19) fashioned on the periphery of the base (1).
 4. Device according to claim 1, characterized in that said means are constituted by means making it possible to slave the rotation of said movable scales (6, 7) to the rotation of the at least one plate (15) or prism.
 5. The device as claimed in claim 4, characterized in that said means making it possible to slave the rotation of the movable scales (6, 7) to the rotation of the at least one plate (15) or prism comprise notched sectors (22) carried by the movable scales (6, 7), notched wheels (24) associated with said notched sectors (22), and at least one notched wheel (25) that can be rendered integral with the plate (15) or with the prism and associated with at least one pinion (27) that can be meshed with one or other of the notched sectors (22).
 6. The device as claimed in claim 5, characterized in that it comprises a number of plates (15) or prisms, of notched wheels (25) and of pinions (26) which is equal to the number of movable scales (6, 7).
 7. The device as claimed in claim 1, characterized in that said plate (15) comprises a recessed part (16), of which an edge (17) is situated on the axis of articulation (T) of the movable scales (6, 7) and a reflecting part (18) on at least one of its faces.
 8. The device as claimed in claim 1, characterized in that said plate (15) is both transparent and reflecting over the whole of its surface.
 9. The device as claimed in claim 1, characterized in that said scales (2, 6, 7) comprise foresights (4, 9, 12) situated on said axes (Y, X, Z).
 10. The device as claimed in claim 2 characterized in that said means for facilitating and curtailing the positioning of the axes (X, Y, Z) are constituted by a graduated ring (19) fashioned on the periphery of the base (1). 